西藏地区季冻土路基冻胀特性现场试验研究

Field Test Study on Frost Heaving Characteristics of Seasonally Frozen Soil Subgrade in Tibet

依托西藏拉妥至芒康公路改建工程,选取现场典型路基断面,在路基不同高度、深度及横向位置处布设了温度-水分传感器、冻胀计,对路基断面处含水量、温度分布及冻胀变形进行了长期监测,研究了三者在时间和空间上的分布情况和变化规律.结果表明:左右路肩及中部测线最大冻结深度分别约为1.25 m与0.85 m;经历一次冻融循环后路基深度-0.5 m上下范围内水分有所积聚,而冻结深度以下土体含水量减小,该区域水分向上发生迁移后部分没有发生回降;冻胀变形过程可大致分为冻胀发展期、冻胀稳定期、冻融交替期、融沉期4个阶段及对应时间段;研究断面-0.5~0 m范围内为显著冻胀区,右路肩(阴面)测线温度振幅、温差及冻结深度最大,阴阳坡效应在该区域类似走向的道路设计中应重点考虑.

Relying on the reconstruction project of Latuo-Mangkang Highway in Tibet,the typical subgrade section was selected,and temperature-moisture sensors and frost heaving meters were arranged at different heights,depths and lateral positions of the subgrade.The water content,temperature distribution and frost heaving deformation at the subgrade section were monitored for a long time,and their distribution and variation laws in time and space were studied.The results show that the maximum freezing depth of the left and right shoulders and the middle survey line is about 1.25m and 0.85m respectively.After a freeze-thaw cycle,water accumulated in the upper and lower range of subgrade depth of-0.5m,but the soil water content decreased below the freezing depth,and some of the water in this area did not fall back after it migrated upward.The process of frost heaving deformation can be roughly divided into four stages:frost heaving development stage,frost heaving stability stage,freezing-thawing alternation stage and thawing settlement stage and corresponding time periods.The range of-0.5~0m in the study section is a significant frost heaving area,and the temperature amplitude,temperature difference and freezing depth of the right shoulder(shadow)survey line are the largest,so the yin-yang slope effect should be considered in the design of roads with similar trends in this area.